This section provides background information related to the present disclosure which is not necessarily prior art.
At present, an optical module of a client operates at an uplink wavelength using the technologies of Dense Wavelength Division Multiplexing (DWDM), and as the DWDM technologies are developing, a tunable laser has become prominent in an intelligent optical network due to its ability to provide an operator with a more flexible light wave at a higher speed. Since the interval between TWDM PON wavelengths in the TWDM PON standard is 100 GHz, i.e., 0.8 nm, and the required precision of the wavelengths is ±12.5 GHz, i.e., 0.1 nm, the optical module of the client may highly demand for the precision of the uplink wavelength.